HAMsmithing July 2017

This is a DIY USB charging cable for my Kenwood TH-F6A/F7E handheld radio.

It is the same concept like the Baofeng USB to 10V charging cables that are found on eBay and amazon. But the virtue of the Kenwood HT is that it accepts a wide array of operating and charging voltage. Plugged to a 12V source it both charges and operates.

On operation it draws 2 amps and that requires a hefty DC-DC converter and will certainly exceed most USB power supply abilities.

So this build is for charging only. According to the item info, it draws about 5 watts (5V @ 1A) and a outputs about 5 (12V @ 0.4A). Which is good enough for emergency charging by the USB powerbanks, that are becoming all the more common.

The Build

It is just what it seems. The DC-DC converter board, a wire soldered terminating in a DC plug, 1.35mm x 3.5mm for the TH-F6/F7.

But on testing I observed that the converter gets quite hot, so an addition of a heatsink on the owner transistor should be added.

Update July the 22th:

I went a bit further with this build. I used a piece of steel as a heatsink. I fixed it in place with Fujik thermal glue while taking care to touch the power transistor on the board. Clear heatshrink was added for protection and good looks but I cut a window for the heatsink.